CICS overview

What CICS is

CICS is IBM's transaction server. It runs COBOL programs that respond to terminal and HTTP requests, handling thousands of transactions per second on z/OS. Banks run their core systems on it.

EXEC CICS

A CICS program talks to the world through EXEC CICS commands instead of OPEN and READ: SEND to write to a screen, RECEIVE to read a field, RETURN to end the transaction:

EXEC CICS SEND TEXT FROM(WS-MESSAGE) END-EXEC. EXEC CICS RECEIVE INTO(WS-INPUT) END-EXEC. EXEC CICS RETURN END-EXEC.

How programs differ

A CICS program never has a PROCEDURE DIVISION opening paragraph of its own in the usual sense: CICS calls it per transaction, there is no STOP RUN, and every request must end with EXEC CICS RETURN. The same division and data rules apply to everything else.

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Article author: Arthur Isaev